The invention concerns track drives intended in particular for propelling all-terrain vehicles such as agricultural, vineyard and oyster-farming tractors or civil engineering and forestry equipment.
In its patent FR-A-2,711,959 (93 13 211), the applicant proposed particularly advantageous modifications for track drives. One essential idea is to provide as a track an endless flexible belt, preferably of a reinforced elastomer material. The track is fitted on the inside with at least one row of lugs arranged in the longitudinal direction of the belt, spaced at a constant pitch and each delimited by two transverse faces forming an angle of between 30xc2x0 and 40xc2x0 in relation to a plane normal to the track belt, and a drive wheel on which the track is wound, and fitted with drive means able to co-operate with the lugs.
Thus a drive wheel comprises a drive zone, generally next to its median plane and perpendicular to its axis of rotation, forming a gear for driving the lugs, with, on either side, rolling support zones for the track known as roll paths. The same applies at least to certain idler wheels which co-operate with the track, except of course for the drive gear function. The roll paths play a significant role in supporting the track and where applicable maintaining it on its drive.
A problem arises when stones, pieces of wood, sand, gravel or other similar foreign bodies become enmeshed between the track and a wheel, in particular but not exclusively a drive wheel. In fact a considerable mechanical xe2x80x9coverloadxe2x80x9d on the track can result, often with effects tending to puncture the track and damage its structure.
These effects are relatively poorly known and depend on the shape and number of the foreign bodies thus introduced at a given moment for a given track, their mechanical characteristics and their positional distribution.
The applicant has used wheel scrapers to limit the number of foreign bodies thus present. But this solution has not given complete satisfaction.
The purpose of the present invention is to improve the situation.
The invention comprises a wheel for a flexible track comprising two rolling support zones surrounding a drive zone.
According to a general aspect of the invention, a rolling track comprises a multiplicity of cavities of selected form opening radially towards the outside of the wheel and laterally towards the edge of the wheel so as to promote lateral evacuation of any material or object liable to be caught between the wheel and the track.
The applicant has in fact found that it is possible and even favorable to reduce the active surface of the rolling zones by providing cavities which, in combination with the movement of the wheel, allow considerable limitation of the accumulation of debris between the wheel and the track. The track positioning and its running smoothness are not affected significantly.
In general the rolling paths are of circular cylindrical shape. The cavities form recesses with angular spacing, preferably regular, at least statistically.
In one embodiment the rolling paths are defined by flanks on either side of the core of the wheel (central plane). The cavities are arranged in the outer face of these flanks. The invention also covers the combination of a track, in particular the endless belt type, with at least one wheel as defined above, and also any vehicle fitted with at least such a combination of means (in principle two).